The U.S. reportedly killed three al Qaeda members in a drone strike Monday, the first strike on militants since Yemen’s U.S.-backed president resigned last week, according to Reuters. The strike is a sign that the U.S. air campaign in Yemen will continue without the blessing of President Abed Rabbo Mansour Hadi, who was a leading U.S. partner against the militant group.

Hadi’s resignation left a power vacuum that both the Shiite Houthi rebels and al Qaeda in the Arabian Peninsula (AQAP) hope to fill. This has made the U.S. efforts to eradicate AQAP, thought to be the strongest branch of al Qaeda and the most direct threat to the U.S, even more essential.

"In the short term, this political crisis in Sanaa is a boon to al Qaeda, because as long as the political crisis is going on, everybody's attention and focus is there, and that means the attention and focus of the Yemeni government is not on al Qaeda," CBS News national security contributor Michael Morell, a former deputy director of the CIA, told CBS News last week.

U.S. officials did not respond to International Business Times' request for confirmation of the drone strike. The U.S., however, has been using drones in Yemen for years.

"This strategy of taking out terrorists who threaten us, while supporting partners on the front lines, is one that we have successfully pursued in Yemen and Somalia for years," President Barack Obama said, comparing U.S. counterterrorism policy in Yemen to that in Iraq and Syria against the Islamic State group.

AQAP has the capacity to carry out large-scale massacres in the West and, in the past, has provided attackers with training, intelligence and weapons. The group also took responsibility for the dual attacks in Paris this month that left 17 dead.  

"If it is true, it is a very significant move,” Bob Milton, a retired commander of the London Metropolitan Police Service in the U.K. and now a counterterrorism professor at Bay Path University, told IBTimes after the attack in Paris. “It’s another step forward for the ambitions of al Qaeda in the Arabian Peninsula and should be taken very seriously.”

AQAP's immediate enemies on the ground, however, are the different factions battling in Yemen. Yemen has become a focal battleground for the Sunni-Shiite conflict sweeping the region and has pinned the Sunni kingdom of Saudi Arabia against the Shiite government of Iran. The Houthi rebels, backed by Iran, seized the capital last week, forcing Hadi’s Saudi and U.S.-backed Sunni government to resign.

Karen Elliott House, the author of “On Saudi Arabia: Its People, Past, Religion, Fault Lines -- and Future,” recently told IBTimes that “this power struggle between Saudi and Iran is the key reason there is so much chaos and conflict in the region now.”